Remote plugging device for wells

ABSTRACT

Remote cement plugging device ( 10 ) and method of use. The device has at least one means ( 60 ) for perforating at least one hole through a wall of a first well casing, and means to inject cement into an annulus between the inner well casing and a second well casing. The perforating means has at least one punch ( 65 ) actuated by compressed fluid (hydraulic, pneumatic) to form the hole(s), and thereafter the cement is delivered to the annulus between the inner and outer/intermediate casings to form the cement plug without the need to withdraw the device from the well casing.

FIELD OF THE INVENTION

The present invention relates to the plugging of hydrocarbon wells,particularly subsea hydrocarbon wells, when barriers must be maintainedbetween the hydrocarbon formation and the surface to prevent hydrocarboncontamination by leakage from the well.

BACKGROUND OF THE INVENTION

In the field of subsea oil and gas production there are regulations thatrequire barriers to be maintained between the oil and/or gas formationand the surface.

During abandonment of subsea wells the barrier system must be maintainedto ensure that any residual oil or gas in the formation does notdissipate from the well leading to a potential pollution event, with theassociated environmental and social impact.

Barrier systems for offshore wells consist of active and passivesystems, with the passive systems a physical barrier is maintainedbetween the formation and the seabed. Active systems are designed thenin the case of an emergency or in unforeseen circumstance the activesystem deploys to provide a barrier between the formation and theseabed.

When abandoning an offshore well the use of active systems to maintainthe barriers between the seabed and the formation is not suitable asthere will be no ongoing maintenance of the barrier. Further duringremoval of the well head of the subsea well one of the barriers coveringthe annulus between the inner casing and the first intermediate casingis removed and needs to be replaced prior to severing the well head.

One way of maintaining the barriers during abandonment of a subsea wellis the use of cement. A cement plug is cast into the central casing andcement is injected into the annulus between the central casing and thefirst intermediate casing. To pump the cement into the annulus it isfirst necessary to provide a pathway for the cement to travel from thecentral casing into to the annulus. This is usually done by the use ofexplosives to puncture holes in the central casing through to theannulus.

When a subsea well is abandoned the use of a jack up oil rig, work bargeor semi submersible has traditionally been used. With the use of thesetypes of vessel, the production of holes in the casing through to theannulus is usually by the use of explosives. There are several issueswith the use of explosives not least of which is the safety aspects.Further a large stable platform must be provided so that explosives canbe safely handled.

The existing methods for subsea intervention and abandonment of wellshave some inherent disadvantages including the use of large vessels sothat explosives can be used, these vessels tend to be slow moving, takea relatively long time to reach offshore oil and gas fields and areexpensive to operate while on station.

In order to alleviate problems of the cost and time taken to get a largework platform on a station, the use of a work boat is desired. Problemswith using a work boat arise when using explosives, so alternativemethods and means of providing holes in the casing and injecting cementare required.

The reference to any prior art in this specification is not, and shouldnot be taken as, an acknowledgement of any form of admission that theprior art forms part of the common general knowledge in Australia.

SUMMARY OF THE INVENTION

With the aforementioned in mind, in one aspect the present inventionprovides a device for oil field operations including means forperforating holes in a wall of a first well casing and means forinjecting sealant into an annulus between the first well casing and asecond well casing,

including at least one punch assembly, a cutting tool the cutting toolbeing designed to produce a hole in the casing and a sealant deliverymeans.

wherein the tool is able to perforate the holes and deliver sealant tothe annulus without the need to withdraw the tool from the well casing.

A further aspect of the present invention provides a remote pluggingdevice for well operations, including at least one perforating means forperforating at least one hole through one or more well casings, andsealant injection means to inject sealant between at least one of saidone or more well casings and at least another of said well casings or afurther well casing,

wherein the perforating means includes at least one punch actuated bypressurised fluid to perforate the at least one the hole, and thereafterthe sealant is delivered to the annulus to form the sealant plug withoutthe need to withdraw the device from the well casing.

In another preferred embodiment the device and ancillary equipment isadapted for deployment from a work boat for use in subsea applications.

Another aspect of the present invention provides a remote pluggingdevice for well operations, including at least one perforating means forperforating at least one hole through a wall of a first well casing, andinjection means to inject a sealant into an annulus between the firstwell casing and a second well casing,

wherein the perforating means includes at least one punch actuated bycompressed fluid to perforate the at least one the hole, and thereafterthe sealant is delivered to the annulus to form the sealant plug withoutthe need to withdraw the device from the well casing.

Preferably the sealant is cement based, or may be a none setting mediumsuch as drilling mud.

Actuation of the punch(s) by compressed fluid advantageously avoids theneed for explosive charges to effect perforation.

The at least one punch may be actuated by hydraulic or pneumaticpressure.

The at least one punch may be extended or retracted by at least onedouble acting hydraulic or pneumatic piston, which provides positiveactuation and retraction to assist in ensuring that the perforator(s)is/are retracted so that the sealant can flow through theperforation(s). Alternatively, the at least one punch may be extended byhydraulic or pneumatic pressure and retracted by at least one resilientbiasing means, which simplifies the means of return actuation, such asby return spring(s).

Preferably there may be one or more outlet/ports for sealant flowprovided adjacent at least one of said at least one perforation means.This helps to ensure that sealant flow readily reaches theperforation(s) and reduces the overall amount of cement required.

At least one packer assembly may be provided, whereby, when the packerassembly or assemblies is/are expanded to hold the device by pressureinside the well casing e.g. by pressure against an interior wall of theinner casing of the well. Such packers may be energized by hydraulic orpneumatic pressure.

Alternatively or in addition, packers may be provided which are selfenergizing. These may expand as a result of initial pressure from apressurized fluid supply line (e.g. from the surface) or fromhydrocarbon escaping through at least one hole made by the device. Theapplied pressure causes the packers to seal the device within the boreprior to the sealant being pumped into the hole(s).

The device may include at least one fluid pressure accumulator,preferably hydraulic or pneumatic accumulator(s), within or proximate toa leading nose end of the device, the accumulator providing fluidpressure to the at least one packer assembly in the event of a failureof the device. Fluid pressure may be supplied from the hydraulic orpneumatic supply used to actuate the perforation means.

At least two of the perforation means may be spaced apart such that thedistance between a first punch of a first perforation means and a firstpunch of a second perforation means is greater than a length of couplingmembers used to couple together lengths of well casing.

One or more of the punches may have a breakaway shaft such that in theevent of the punch being jammed in the perforated hole, the piston andbase of the punch can be positively retracted and a working end of thepunch sheared off.

At least one of the punches may be retained to the piston by a quickrelease means, such as by a quick release ring, clip or other retainer.

At least one resilient packer may be provided which absorbs shockinduced on the respective punch during perforation of the casing.Silicon rubber, rubber, nitrile, or the like, or combinations thereofmay be used.

The perforating means may be adapted to perforate consecutive holesthrough multiple casing walls, one after the other. That is, where thewell has multiple casings one within another, the perforator may, forexample, perforate a hole through more than one casing to set a sealant(e.g. cement) plug between the first and/or second and third concentriccasings.

A further aspect of the present invention provides a method of sealing awell riser, including the steps of;

a) inserting a remote plugging device into a riser;

b) supplying compressed fluid to the plugging device;

c) perforating at least one hole through at least a first well casingusing at least one respective punch actuated by the compressed fluid;and

d) pumping a sealant through said at least one hole into an annulusbetween the at least one first casing and a second or intermediatecasing to form a plug seal.

The method may further include the steps of perforating one or moreholes with a respective at least one punch, and leaving at least onesaid punch extended to act as an anchor for the device. Thus, one ormore punches may remain unretracted to anchor the device. There can besignificant hydrocarbon pressure on the device when a hole is perforatedthrough the casing, and the unretracted punch(es) may act as a secondarylock to hold the device in place. Also, in the event that the deviceneeds to be abandoned within the well for any reason, this anchoringarrangement can assist in maintaining the device in place. Anaccumulator may be employed to provide sufficient pressure to maintainthe at least one punch extended. A one way or check valve may beemployed to prevent pressure loss once the hydraulic or pneumatic feedis removed from the device.

The method may include withdrawing the at least one punch from at leastone respective hole. However, it is envisaged that the device may pumpfluid around, through, or a combination thereof, the at least one punch;Hydraulic fluid may be used to actuate the punch(s). Preferably thesealant contains cement.

Retraction of the at least one punch may be by hydraulic or pneumaticpressure. Alternatively, extending the at least one punch may be byhydraulic or pneumatic pressure and retraction by resilient biasingmeans.

Perforating said at least one hole may be through a multiplicity of wellcasing walls, and injecting the sealant into the annulus between atleast one of said multiplicity of walls and a further casing wall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an overview of an embodiment of the device.

FIG. 2 shows a section of the entry nose and lower packer assembly ofthe embodiment shown in FIG. 1.

FIG. 3 shows a section of hydraulic punch assembly of the embodimentshown in FIG. 1.

FIG. 4 shows the lower perforation tool of FIG. 1 in more detail.

FIG. 5 shows an alternative embodiment of the device.

FIG. 6 a shows a sectional view of an alternative embodiment of thedevice including spring return hydraulic pistons.

FIG. 6 b shows a perspective view of the complete device of FIG. 6 a.

FIG. 7 a is a perspective view of a perforation assembly of anembodiment of the present invention.

FIG. 7 b is a sectional view of the embodiment shown in FIG. 7 a.

DETAILED DESCRIPTION

The invention will now be described with reference to the accompanyingfigures. Referring first to FIG. 1 that shows an overview of the remoteplugging device herein after referred to as the “tool”. Whilst cement isreferred to hereinafter as the sealant, it will be appreciated thatother sealants may be employed, such as drilling mud.

The construction of the tool 10 is based on modular construction methodsso that individual components can be replaced if they are damaged duringan offshore campaign. Other possible arrangement of the components arepossible provide that they allow for the operation of the tool 10 suchthat the casing is perforated and cement is injected into the annulus.Only a typical example is described in the following detaileddescription.

The overall layout of the tool 10 includes of an entry nose 20 at aleading end 25, designed to allow the cement injection tool 10 to beinserted into a subsea well. The entry nose 20 is connected to a lowerpacker mandrel 30 that has a packer assembly 40 fitted. This packerassembly 40 is designed so that when the tool 10 is inserted into theinner casing of the subsea well, the packer assembly 40 can expand andhold the tool 10 in place and seal the tool 10 in the casing. The lowerpacker mandrel 30 is connected to a hydraulic module 50 at the hydraulicmodule first end 52.

The hydraulic module 50 consists of a number of punch assemblies 60 withpunches 65. The punch assemblies 60 are arranged circumferentiallyaround the hydraulic module 50 and are designed so that they can punchholes in the inner casing. It will however be appreciated that at leastone said punch may be used to perforate through more than one casingwall, such that sealant can be pumped into the annulus or cavity betweenfurther casings e.g., between the inner and intermediate casing, andbetween the intermediate casing and an outer casing.

At the hydraulic module second end 54, there is a cement exit port 75.At the hydraulic module second end 54 there is an upper packer mandrel80 which includes a packer assembly 90 to seal the tool 10 into the wellinner casing attached to the second end 81 of the upper packer mandrel80 there is a breakaway barrier 70. On the upper most portion of thetool 10, there is a hydraulic hose guide 100 and lifting points 110connecting the cement injection tool 10 by a lifting cable and hydraulicand services lines to the boat.

As shown in more detail in FIG. 2, the entry nose 20 is designed with ataper 22 at the leading end thereof to allow for positioning the tool ina subsea well and to guide the tool 10 in to the well inner casingduring deployment of the tool 10. The entry nose 20 has also beendesigned to incorporated a hydraulic accumulator 25. The hydraulicaccumulator 25 is used to provide hydraulic pressure to the packerassemblies 40, 90 in the event of a failure in the tool 10 necessitatingabandonment of the tool 10 in the well. The hydraulic accumulator 25allows for the tool 10 to act as a barrier in the event that the tool 10needs to be abandoned. The entry nose 20 may be held by a threadedportion 28 to the first end 31 lower packer mandrel 30.

The lower packer mandrel 30 is generally hollow but could be made of arange of materials or densities to provide the desired buoyancycharacteristics of the tool 10. The packer assembly 40 associated withthe lower packer mandrel 30 is designed that once subjected to ahydraulic pressure, the packer assembly 40 can expand and seal againstthe inner casing. The pressure that can be applied to the packerassembly 40 is approximately 5000 psi, but could be more on someapplications. At the second end 32 of the lower packer mandrel 30 thereis packer mandrel threaded portion 33 that connects the lower packermandrel 30 to the hydraulic module 50 at the hydraulic module first end52.

The hydraulic module 50 is the module that contains active hydrauliccomponents and the tooling required to perforate holes through the wellinner casing. The hydraulic module 50 includes at least one hydraulicpunch assembly 60, though there may be as many as ten or more hydraulicpunch assemblies 60. The spacing and orientation of the hydraulic punchassemblies 60 is such that holes can be perforated through the innercasing in different locations around the circumference of the innercasing and in different positions vertically along the inner casing.

In a preferred embodiment, the punch assemblies 60 are spaced apart suchthat the distance between a first punch 62 and second and subsequentpunches 65 is greater than the length of the coupling members not shownnormally used to couple lengths of well casing together. This is so thatwhen the tool 10 is inserted into an inner casing holes can still beperforated even if one punch assemblies 60 is behind a coupling member,the remaining punch assemblies 60 will not coincide with the couplingmembers and therefore will able to perforate the inner casing.

At the second end of the upper punch mandrel 82 there is a breakawaybarrier 70. This breakaway barrier 70 is designed such that should thedevice need to be abandoned in the well due to unforeseen circumstances,the well remains plugged such that the contents of the well will notleak. The breakaway barrier 70 has hydraulic lines and coupling checkvalves connected so that in the event of a breakaway event, thehydraulic pressure in the packer assemblies 40 90 remains constant,thus, ensuring that the packer assemblies 40 90 are held firmly in placeagainst the inner casing. The breakaway barrier 70 is designed to havelocking pins to take a predetermined load. These locking pins aredesigned to have sufficient strength that the tool 10 can be extractedfrom the inner casing even with residual cement surrounding thehydraulic module 50 yet can be broken away in the event that the tool 10must be abandoned. A typical breakaway load is 25 tons but this loadcould be varied depending on the application of the tool 10.

The breakaway barrier 70 also includes a check valve on the sealant linethat may be actuated by hydraulic pressure or automatically actuated(e.g. by spring loaded pressure). This check valve may be located in theupper packer mandrel 80 the check valve can be a normally closed checkvalve that is actuated by hydraulic pressure, or pneumatic pressure.

The tool may be provided with a number of lines that communicate withthe vessel (not shown). These lines will include hydraulic, control,monitoring and bypass lines. These line allow for the tool 10 to beoperated from the vessel and parameters such as the pressure in the wellcan be monitored.

Referring now to FIG. 3, the hydraulic punch cylinder assemblies 60include two way hydraulic pistons 61 capable of at least 5000 psi ormore, though the upper pressure limit may vary depending on the expectedloads required to perforate the casing. The hydraulic pistons are fittedwith punches 65 used to perforate the inner casing. The two-way pistonis selected to ensure that the punch 65 can be retracted once a hole hasbeen perforated in the inner casing. The two way type of hydraulic punchassembly includes a hydraulic feed 69 to provide hydraulic pressure toretract the piston

The punch 65 is manufactured of a tool steel and is used to punch holesin the inner casing. The punch 65 is designed with a breakaway shaft 66so that in the event of the punch 65 being jammed in the perforated holein the inner casing the hydraulic piston 61 can be positively retractedand the punch 65 sheared. The punch 65 is held into the punch pistonassemblies with a quick release ring 67. This quick release ring can beremoved to allow for field removal and replacement of the punch 65 inthe situation where multiple wells are being abandoned and a punch 65requires replacement. In the case of punches used for anchoring thedevice, these would preferably be non-breakaway punches, such that thepunches remain extended to hold the device in place.

Behind the quick release ring 67 is a resilient packer 68 that acts toabsorb the shock induced on the punch 65 when the holes are produced.The resilient packer 68 may be made out of a range of materials capableof absorbing a shock load. Preferred materials are ultra high molecularweight synthetic materials, such as PEEK, UHMPE, HFPE, or Nylon etc, orother water stable dense synthetic materials.

In an alternate embodiment, the hydraulic pistons 61 are not two wayhydraulic pistons but use the pressure of the cement or formation toretract the hydraulic pistons 61 once the holes have been punched. In apossible variation the use of spring actuated hydraulic pistons may beused when the tool 10 is intended to be abandoned in the well.

FIG. 4 shows the hydraulic module 50 of the lower perforation tool ofFIG. 1 in more detail. The module that contains active hydrauliccomponents and the tooling required to perforate holes through the wellinner casing. The hydraulic module includes at least one hydraulic punchassemblies 60, and one of the cement feed outlets 75.

FIG. 5 shows an alternative embodiment of the device including first 60a and second 60 b lower perforation assemblies, and first 60 c andsecond 60 d upper perforation assemblies. These are connected via acable link 110 of variable length “D” to suit a particular application.Upper cup packer 112 a and lower cup packer 112 b are provided. Theseact to provide a seal between the device and the casing wall to preventcement from flowing beyond the packer. They also provide a pressure sealif hydrocarbons present after perforating would otherwise leak out.

Upper and lower bore supply ports 114 are provided. These ports supplycement respectively to the upper and lower sections of the device.

FIGS. 6 a and 6 b shows a further embodiment including single actingspring biased hydraulic punches 65 a-65 d. The punches are hydraulicallyextended to create holes through the inner casing of the bore, and arebiased by spring pressure to the retracted position shown in thefigures.

FIGS. 7 a and 7 b show one of the hydraulic perforation assemblies 60.FIG. 7 a is a perspective view of the assembly with a punch 65. Insectional view FIG. 7 b of the assembly 60, with the hydraulic piston 61b retracted within the body 61 a of the assembly. The punch 65 isretained in place by a screw fit ring 120 analogous to the quick releasering in FIG. 3. Grub screws 122 a and 122 b retain the hydrauliccylinder 61 a within the casing 124.

A hydraulic release shackle 116 is provided (analogous to the breakawaysystem previously described), which allows the device to be completelyuncoupled i.e. in the event that the device becomes unrecoverable fromthe well. Annulus bore pressure monitoring and bleed off ports areprovided.

In operation the cement injection tool 10 is lowered from a vessel 1 andwith the assistance of divers or an ROV is positioned into the innercasing of a subsea well. Once the cement injection tool 10 is loweredand is positioned, hydraulic pressure is applied forcing the packerassemblies 40, 90 to lock the cement injection tool 10 against the innercasing walls. The packers are then tested to ensure there are no leaks.Hydraulic pressure is then applied to each of the punch assembly 60 inturn resulting in a series of holes being perforated in the innercasing. Any pressure from the annulus is then bled off in a controlledmanner either into the sea or into a tank on the vessel. Ideally thehole punching will result in multiple holes being punched in the innercasing, the holes being evenly distributed around the circumference andalong a length of the inner casing.

Once the holes in the inner casing have been perforated, a cementinhibitor is injected to inhibit the setting of the cement in thecrevices and joints surrounding the packer assemblies and the punchassemblies. The inhibitor is injected through the cement injection port54, it then travels down past the hydraulics in the hydraulic module 50.

After the inhibitor has been injected, cement is injected through thecement injection port 54 and flows around the hydraulic module 50 andthrough the holes punched in the inner casing into the annulus betweenthe inner casing and the first intermediate casing. Once the cement isinjected into this annulus and pressure tested, the packer assembliesare released and the cement injection tool 10 is extracted.

The punch assembly 60 includes hydraulics specifically designed for thisapplication, which include a double acting hydraulic piston 61 (positivedisplacement and retraction piston). This is designed so that the punch65 can be forcibly retracted from the inner casing in the event of aproblem. The punch 65 is inserted into a hydraulic ring and is held inplace by a shock absorbing ring 66 and a punch retaining member 67.

Variations and modifying are possible to the tool 10 that will stillfall with the scope of the invention.

1. A remote plugging device for well operations, including at least oneperforating means for perforating at least one hole through one or morecasings of a well, and sealant injection means to inject sealant into anannulus between at least one of said one or more well casings and atleast another of said well casings or a further well casing, wherein theperforating means includes at least one punch actuated by pressurisedfluid to perforate the at least one hole, and thereafter the sealant isdelivered to the annulus to form a sealant plug without need to withdrawthe device from the one or more well casings.
 2. A device as claimed inclaim 1, wherein the at least one punch is actuated by hydraulic orpneumatic pressure.
 3. A device as claimed in claim 1, wherein the atleast one punch is extended and retracted by at least one double actinghydraulic or pneumatic piston.
 4. A device as claimed in claim 1,wherein the at least one punch is extended by hydraulic or pneumaticpressure and retracted by at least one resilient biasing means.
 5. Adevice as claimed in claim 4, wherein the at least one resilient biasingmeans includes at least one return spring.
 6. A device as claimed inclaim 1, further including an outlet for sealant flow provided adjacentone of said at least one perforation means.
 7. A device as claimed inclaim 1, further including at least one packer assembly whereby, whenthe device is inserted into the well, the at least one packer assemblyis expanded to hold the device by pressure against a bore of the one ormore well casings.
 8. A device as claimed in claim 7, including a fluidpressure accumulator provided within or proximate to a leading nose endof the device, the accumulator providing fluid pressure to the at leastone packer assembly in the event of a failure of the device.
 9. A deviceas claimed in claim 7, wherein the at least one packer assembly isactuated by compressed or pressurised fluid.
 10. A device as claimed inclaim 9, wherein the compressed or pressurised fluid is a hydraulic orpneumatic supply.
 11. A device as claimed in claim 1, wherein said atleast one punch includes a breakaway shaft such that in the event of thepunch being jammed in the hole, the punch can be positively retractedand a working end of the punch sheared off.
 12. A device as claimed inclaim 1, wherein the at least one perforation means includes at leastone resilient packer that absorbs shock induced on the punch when thecasing is perforated.
 13. A device as claimed in claim 12, wherein theat least one resilient packer is formed of silicon rubber, rubber,nitrile, PEEK, UHMPE, HFPE, Nylon, other ultra high density syntheticmaterial, or combinations thereof.
 14. A device as claimed in claim 1,wherein the perforation means is arranged to consecutively perforateholes through a multiplicity of well casings of said one or more wellcasings, and the sealant is arranged to be injected between at least oneof said multiplicity of well casings and said further well casing.
 15. Amethod of sealing a well riser, including the steps of: a) inserting aremote plugging device into a riser; b) supplying pressurised fluid tothe plugging device; c) perforating at least one hole through at least afirst well casing wall using at least one respective punch actuated bythe fluid; and d) pumping a sealant through said at least one hole intoan annulus between the first casing wall and an outer casing or anintermediate casing to form a plug seal.
 16. A method as claimed inclaim 15, wherein the sealant contains cement or drilling mud.
 17. Amethod as claimed in claim 15, further including the step of retractingthe at least one punch by hydraulic or pneumatic pressure, or by usingat least one resilient biasing means.
 18. A method as claimed in claim15, further including retaining at least one said at least one punchextended after perforating the casing.
 19. A method as claimed in claim15, wherein: the step of perforating said at least one hole includesperforating through a multiplicity of well casing walls including saidfirst well casing wall; and the pumping step includes injecting thesealant into the annulus being between at least one of said multiplicityof well casing walls and said outer casing or said intermediate casing.20. A method as claimed in claim 15, further including utilising atleast one packer to provide an initial seal between the device and thefirst well casing against hydrocarbon leakage prior to pumping sealantinto the at least one hole.